I still think DD wouldn't really grasp it. She never really watches me that much. Hmm. Maybe I should actually attempt it though.
Maybe keep it up with just one main sign, keep it fun and you will get there... My DD1 sounds a bit like yours, never watching I think this is the reason I gave up early on. DD1 was never the type to engage in much as an infant, not so keen on peek-a-boo let alone signing. When she worked out the significance at an older age there was no stoping her. My DD2 is much more engaging and interested, hence, I believe, has picked it up much faster.